This invention relates to a source liquid supply apparatus having a cleaning function, to a method for detaching the source tank from said supply apparatus, and to a method for cleaning a source liquid feed conduit. More particularly, this invention relates to the structure of an apparatus for supplying a source liquid, such as a chemical reagent, to a particular facility, for example, to a metalorganic chemical vapor deposition (MOCVD) apparatus. The invention additionally relates to a maintenance technology for said supply apparatus.
The equipment used to fabricate semiconductor devices and electronic devices and instruments frequently employs source liquids in the form of difficult-to-handle chemical reagents whose residues are difficult to remove simply by a gas purge. Once such a source liquid has passed through, for example, a manifold or vaporizer, the interior thereof cannot be satisfactorily treated by purging and cleaning with just a simple gas purge cycle (repetitive pressurization with gas and vacuum exhaust) when it is desired to carry out maintenance or exchange or alter the reagent. A known technology that addresses this problem comprises the use, in addition to the gas purge, of a solvent as a cleaning fluid in order to achieve good purging and cleaning of the target compartment.
An apparatus that employs this particular technology is disclosed in U.S. Pat. No. 5,964,230. This apparatus, which carries out solvent-based purging and cleaning of a chemical-handling manifold, introduces solvent into the manifold through a nozzle disposed coaxially with respect to the manifold and employs a mechanical scrubbing operation in addition to residue dissolution.
U.S. Pat. No. 6,033,479 discloses a process gas delivery apparatus for MOCVD applications that employs an auxiliary cleaning apparatus. A slanted cleaning fluid feed pipe is provided in this system in order to feed cleaning fluid into the process gas delivery apparatus and for discharge of the waste cleaning fluid. This system also contains an optical sensor in the process gas feed pipe in order to determine the maintenance time automatically. This optical sensor can be used both to detect the accumulation of deposited material in the piping and to detect cleaning fluid remaining within the piping after the cleaning process.
U.S. Pat. No. 5,362,328 discloses an apparatus and method for feeding source reagent in vaporized form into a CVD process compartment. In this case, an auxiliary cleaning apparatus is used in order to protect the source reagent vaporizer from the negative influence of solid deposits produced during the CVD process. For example, when it is desired to feed relatively nonvolatile source reagent to the CVD process compartment, the vaporizer may be configured with a large surface area having a high heat transfer efficiency. When such a vaporizer is used in a CVD system, by-products are produced in the vaporizer section from the source reagent, which causes clogging and lowers the vaporizing efficiency. The technology disclosed in U.S. Pat. No. 5,362,328 solves these problems by implementing a periodic cleaning of the vaporizer with an auxiliary cleaning apparatus.
U.S. Pat. No. 4,738,693 (Japanese Laid Open (Kokai or Unexamined) Patent Application Number Sho 64-27616 (27,616/1989)) teaches an apparatus for distributing and purifying semiconductor source reagents. This apparatus is provided with a receptacle and valve block that can be joined to each other in a leaktight manner. The valve block is provided with first and second ports for feeding source reagent and with a purge port for effecting purging. Prior to feeding source reagent, the purge port is opened—while the first and second ports are closed—in order to eliminate gas remaining in the dead spaces from the first and second ports and the gas flow passages.
An apparatus for reagent supply is disclosed in U.S. Pat. No. 6,199,599 (issued 13 Mar. 2001); this apparatus employs at least three purge sources for the purpose of purging reagent from the piping system. For example, a vacuum source, solvent source, and inert gas source are used as three purge sources, wherein the solvent is expelled from the system accompanying feed of the inert gas.
A problem common to the type of prior art systems under consideration, including the systems taught in the United States patents listed above, is the presence of a difficult-to-purge dead space in the vicinity of the joint or connection between the source tank and the conduit for feeding source liquid to the process apparatus. As a consequence, even after the piping has been purged, substances such as source liquid, cleaning fluid, and semidecomposed materials therefrom can easily remain within this dead space. When, for example, these residues come into contact with air when the source tank is exchanged, they form difficult-to-remove substances that clog the piping or produce substances that poison the process. Taking as an example the use of PET (pentaethoxytantalum) to form high dielectric films, upon contact with air this reagent reacts with O2 and H2O to form a gel-like material. In the case of TiCl4 the reaction of this compound with H2O results in the production of HCl, a chemical that lowers the film-forming rate.
This invention was developed in view of the problems delineated above for the prior art. An object of this invention is to provide a source liquid supply apparatus that incorporates a cleaning function and that avoids leaving source liquid- and/or cleaning fluid-derived residues in the vicinity of the joint or connection region between the source liquid feed conduit and the source tank. An additional object of this invention is to provide a method for detaching the source tank from the foregoing apparatus. A further object of this invention is to provide a method for cleaning a source liquid feed conduit.